If she was asking about the doctor in voyager then surely she would have wrote that !!!!
Data has indeed sung opera in a number of next generation episodes and also sang a piece at the beginning of the movie Insurrection.
Unfortunately I cannot remember the piece in Insurrection although it is mentioned in the film. As for the Next Generation episodes... Which one do you mean? Have you a title or remember the premise of the film?
Nicky, try this on,
Stephen Schwartz, who wrote the music and lyrics for Geppetto, says that there "will be a soundtrack album, and Brent's number, which is one of the high points of the show in my opinion, will be included. His number is entitled 'Bravo, Stromboli,' and it is sort of a send-up of 'The Barber of Seville.' Brent sings in a sort of mock-opera tenor and hits a high G, which he holds for an inordinately long time. He's very good and very funny, and I think a lot of his fans, particularly those who know him primarily through Star Trek, will be surprised at how well he sings"